DSCC states that following the launch of the first foldable OLED devices in 2019, the market is expected to experience a very fast growth - by 2022 the market will reach 63 million units, up from 3 million in 2019 (a CAGR of 173%). In terms of revenues, the market will reach $8.9 billion by 2022 (151% CAGR).
It is a bit confusing that DSCC segments this market by device type - as foldable OLEDs will probably merge these segments together (i.e. a phone/tablet, tablet/notebook, wearable/smartphone, etc).
The first wave of foldable devices is expected in early 2019 (or maybe by the end of 2018). The first devices are expected to be Samsung's Galaxy F (smartphone/tablet), the Nubia Alpha (bracelet/smartphone) and Huawei's upcoming phone/tablet. These will probably be joined by more devices that haven't been announced yet.
Leading foldable OLED producers seem to be Samsung Display, Visionox (who will supply to Nubia) and BOE (who will supply to Huawei).